It is known to provide a shaver or razor that relies on a laser for cutting hair rather than an arrangement of cutting blades. Shavers without blades have fewer moving parts and so wear is reduced, which provides an advantage over mechanical shavers. Furthermore, the use of a laser can reduce skin irritation as there are no sharp objects that contact the skin surface. Laser shavers work by either optical absorption or by creating laser induced optical breakdown of the hair. With optical absorption, hair is exposed to a laser beam and absorbs the energy of the beam, causing the hair to be vaporised and/or severed. With laser induced optical breakdown of the hair, the hair is cut by cavitation and/or the generation of shockwaves.
Shaving performance is typically measured by two criteria closeness of shave and irritation of the skin. Therefore, a good performing shaver should minimise the remaining hair length by positioning the laser as close as possible to the skin. However, this may cause more skin irritation if heat and energy from the laser is incident on the skin. It is necessary to protect the skin from contact with the laser beam to avoid damaging or irritating the skin being shaved. Hair trimmers or groomers are used to trim hair to a constant length, so although closeness is not a major performance factor, uniformity of remaining hair length is desirable.
It is known, for example from WO 92/16338, to generate a laser beam that is positioned parallel to the skin and perpendicular to the stroke direction to cut hairs as the shaver is moved over the skin. However, Gaussian theory dictates that laser beams have a natural intensity variation along their length. Furthermore, when hair is cut with a laser a number of parasitic physical and chemical phenomena may occur that impede the hair cutting process.